Beam type electron discharge device



Jan. 25, 1949. r v P. e. CHVEVIGNY I 2,459,792

BEAM TYPE ELECTRON DISCHARGE DEVICE Filed July 8, 1944 271:] a $13k J19 P404 cmswa/vy ATTORNEY Patented Jan. 25, 1949 2,459,7e2 BEAM TYPE ELECTRON DISCHARGE DEVICE Paul Georges Chevigny, New York, N. Y., assignor to Federal Telephone and Radio Corporation,

New York, N.;Y., a corporation of Delaware .Application July 8, 1944, Serial No. 544,053

7 Claims. 1

This invention relates to electron discharge devices and particularly those of the beam type.

In electron discharge devices, electrons are normally emitted from the cathode in all directions normal to the surface thereof, but not all this emission serves a useful function. Indeed, emission in certain directions is not only useless but harmful in that it adversely affects the operating characteristics of the electron discharge device.

An object of the present invention is the provision of an electron discharge device having a cathode whose emissive characteristics at various portions of its surface differ in accordance with the requirement of the electron discharge device, for example at certain portions thereof there is substantially no electronic emission.

In beam type electron discharge devices, electronic emission from the cathode in a direction other than along the paths of such beams, serves no useful function, and moreover such unnecessary emission introduces complicating factors adversely affecting the optimum operational characteristics of such devices. Accordingly another object of the present invention is the provision in a beam type electron discharge device having predetermined beam paths between the cathode and anode of a cathode which emits electrons only from those surfaces in the direction of said paths.

Other and further objects and advantages of the present invention will become apparent, and the foregoing will be best understood from the following description of an embodiment thereof,

reference being had to the drawing in which:

Fig. 1 is a view, partly in elevation, partly in section, of an electron discharge device embodying my invention;

Fig, 1A is a partial section taken along the line IA-IA of Fig. 1; and

Fig. 2 is an enlarged metallurgical cross section of one of the filament elements, this view being exaggerated to bring out the details thereof.

Referring now to Fig. 1, numeral I generally designates a beam type power tube. The tube envelope '2 includes an upper insulating portion 3 and a lower cylindrical insulating portion 4 joined together by a generally annular member 5 for mounting the grid structure. The member 5 may be of copper and is sealed to the upper and lower portions 3 and 4 of the envelope by any suitable means such as knife edge seals 6. Passing through and sealed in the upper portion 3 of the envelope 2 are the cathode support members I and 8 which also serve as current carrying leads. Respectively attached to the inner ends of cathode support members or leads I and 8 are metallic rings 9 and I 0, each of which in turn has attached thereto a plurality of conducting rods II and I2 respectively. Depending from the rods I I and I2 is a cylindrical cathode I3 comprised of a plurality of filament elements I4, each of said filament elements I4 being parallel to the next one and arranged in a circle concentric with the central longitudinal axisof the tube. Filament elements I4 are also spaced an equal distance apart, the lower ends I5 of said elements l4 being bent inwardly and gathered in and attached to a castellated nut I6 which serves to hold the elements in place, and moreover electrically connects the elements together at their lower end.

Alternate ones of the elements I4 are connected to rods II, the rest of said elements I4 being connected to rods I2.

I It will thus be seen that filament current flows, through leads 1, ring 9, rods I2 and through alternating ones of filament elements I4 which are connected to rods I I to the castellated nut I6 and then out through the other of said elements I4 which'are connected to rods I2, through ring I0 and lead 8.

The anode electrode Il may be formed from a solid block of metal, preferably copper. A suitable knife edge I8 is formed on the outside of the anode structure in order to seal the anode to the lower end of the lower cylindrical portion 4 of the envelope and thus complete the tube envelope. The active portion of the anode or that portion thereof which receives the electron current from the cathode is a cylindrical surface I9 which may' be formed by boring a hole in the end of the copper block. The length of this active surface I9 is preferably substantially equal to the length of the cathode facing it. The active surface I9 is concentric with the cylindrical cathode I3. The lower portion 20 of the copper block may be provided .with any suitable cooling means (not shown) such as vanes adapted to be cooled by either blasts of air or by circulating liquid medium. 4

Tube I also includes two grid electrodes 2| and 22 which are supported from the annular member 5 by means of conical conducting or supporting members 23 and. 24, conical members 23 being electrically connected to the annular member 5 and conical member 24 being electrically insulated from said member 5 by suitable Washers 25 and connected to a lead-in wire 26 passing through an opening 21 in the annular member 5 and through a pipe 28 which is hermetically sealed by a glass bead 29. Ring 5 serves as the external terminal for grid 2! and lead-out wire 26 serves as the external terminal for grid 22. The aforedescribed grid structure and leads are more fully described in my joint c'opending. application for "Electron discharge devices, filed June 26, 1944, Serial No. 542,076, now U. S. Patent Number 2,438,899.

Grids 2| and 22 each consist of a plurality of parallel bars 3!] and 3| arranged in circles concentric with the cylindrical cathode l31'andthe active anode surface I9. These bars ;and 3| are held in place by suitable spacingrmembers .32 and 33 at one end and are sealed at their other ends to their respective conical supporting mem bers 23 and 24.

Referring now to Fig. 1A, it will be seen that each of the bars 30 of grid2l is radially aligned with its corresponding one'of bars 3| of grid 2-2. This arrangement serves to provideuninterrupted radial paths 34 between each pair of aligned bars extending from the active anode surfaceiQ .to one side of the filament elements 14, each of which elements M is facing one of said paths34 in a direct uninterrupted line with the activesurface 19 of the anode As set forth hereinabove in-the objects of this invention, it is desired that the filamentelements l4 should only emit electrons from the surface thereof facing the active surface .l.9.of theanode along the uninterrupted path. The surface.,35 vof the filament elements I4 facing the activesurface IQ of the anode may be a flat surfaceasillustrated in Fig. 2 so that electrons emittednormal to said surface would tend to go in a beam along path 34 towards the anode and would not spread out laterally as much as would tend to be the case if said surface 35 were curved. .Suchastructure results in the filament element having a segmental cross section. While surface-35 of filament element I4 is to emit electrons it is desired that the rest of the surface offilament element I4, which may be a curved surface 36, should .not emit substantially any electrons.

, titled Electrode for electron discharge device and method of producing the same, filed May 19,

1944, Serial No. 536,332.

As shown in Fig. 1A, it willbe seen thatwhen the filament elements 14 are arranged inthe tube,

their flat surfaces 35 directly face the anodes along beam paths 34. It will further be seen'that there will be no emission in any of the other directions either towards the center of the .tube or .sidewise, tangentially of thecathodestructure.

While I have described a single specific embodiment of my invention, it will be apparent that details thereof may be varied without departing from the teachings thereof. For example, while I have illustrated my invention in connection with a tetrode, it is obvious that it is equally applicable to a pentode or to the other multielement tubes. Furthermore, while I have shown a birdcage type of electrode assembly, it will be apparent that other forms of assembly may be used embodying my invention.

Accordingly, while I have described above the principles not invention in connection with specificapparatus, it is.tofhe .clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects of my inven- "tion and the accompanying claims.

I claim: I

.1. A beam type electron discharge device com- :prtising an anodasa cathode and at least one control. element, said element being mounted relative to and providing a clear path between said anode andrcathode, said cathode being comprised of a filamentary element having a segmental cross section. and havingelectrically emissive and nonemissive surfaces, said emissive surfaces being flat and facing along the path and all of said nonemissive surfaces being away-from saidanode.

.2. A beam typeelectron discharge device com prising an anode, a-cathode, at least one grid having .a plurality of elements mounted .between said anode. and'cathode, saidelemen-ts-of the grid ,providingatileast one clear ,path betweensaid anode and cathode, said cathode comprising spaced parallel filamentary elements .lying equidistant from saidanode, there beingone of .said filamentary elements for eachpath, said cathode elements having velectronically emissive surfaces and surfaces coated with substantially non-emissive material, the emissive surfaces of saidcathode elements facing toward the anode with an of thenon-emiss'ive surfaces of said cathode lfacing away from saidanode.

3. A beam type electron discharge device according to claim "2, in which the cathode is .of the thoriatedtungsten type whose emissive surface'is carburized' and whose non-emissive surface is .uncarburize'd.

4. A beam type electron discharge device accordingto-claim2, wherein the emissive surface ;of.said cathode is flatand the non-emissive surface iscurved.

:5. Abeam itype :electron discharge deviceraccordingtoclaim 2 wherein thenon-emissivesursface .ofsaidcathodejs covered with a eoatingr'o'f :an emission :inhibiting. material.

6..."A:beam:type electron discharge device comprising-an anode, a cathode, anda plurality of grids mounted between-said anode and cathode, "each-of said grids includingaplurality of grid elements. equally spaced, the corresponding elements ofeach of said grids being aligned and providing clear pathsbetween'the "anode and cathode, said cathode comprisingyspaced parallel filamentary el'ementsjJying equidistant from said away fromsaid' anode.

5 7. A beam type electron discharge device according to claim 6 wherein said electronically emissive surfaces are fiat and said substantially non-emissive surfaces are curved.

PAUL GEORGES CHEVIGNY.

REFERENCES CITED The following references are of record in the filc'of this patent:

UNITED STATES PATENTS Number Name Date 1,529,597 Langmuir Mar. 10, 1925 1,563,547 Gero Mar. 27, 1928 Number Thompson July 26, 1940 

